The present invention relates to an improvement in cup sealed cartridges, wherein a telescoped pusher cup, which is folded back within itself, is employed for the dual functions of sealing propellant gases and propelling an item, such as a piston or a projectile, by the unfolding action of the pusher cup.
Cartridges of the aforesaid type are described in U.S. Pat. Nos. 3,106,131 and 3,404,598. The pusher cup employed in the cartridges of these patents is fabricated of material, such as aluminum, which is capable of permanent plastic deformation, i.e., is substantially self-sustaining in the deformed position and will not self-restore itself to the shape or size it originally held prior to deformation, such as would be effected in elastic deformation. The drawn aluminum cup employed was folded back within itself so that when the cartridge was fired the cup unfolded and pushed the piston or projectile forward. In operation, however, the aluminum pusher cup expanded and remained in the expanded state in the gun barrel, causing it to seize in the barrel and thus rendering its removal very difficult. In an attempt to overcome this problem, the aluminum cup was coined so that the coined disk would blow out when the cartridge was fired and thereby allow the aluminum cup to shrink back from the wall of the gun barrel. This made it possible to remove the cartridge from the gun barrel but prevented the cartridge from smokeless, flashless and noiseless operation. Also, noise radiated through the wall of the aluminum cup.